So I had to put my vita into a DMz to make wipeout work online. Everything else seems fine online with it. So a few questions.

If that address on my vita is in the dmz, is that address going to change and make the dmz no longer "valid",if you will?

Anything else I need to know about this sort of thing. I've been a pc gamer and console gamer for along while. I really never HAD to deal with this kind of thing. Any info would be greatly appreciated. Off to play some wipeout!

Nope, no downside to giving a device a specific IP. When I do this, I usually give the static IPs to the upper end of the DHCP range so it's easier to keep track. For example, my router is 192.168.1.254, my wifi is 192.168.1.253, and then I have a static assigned computer that is 192.168.1.252.